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Biomedical subjects

G Rølla

Publications and source records attributed to G Rølla.

At least 19 recordsLinked to original sources
PubMed1992

The in vivo orthodontic banding model for vital teeth and the in situ orthodontic banding model for hard-tissue slabs.

This paper presents the orthodontic banding model for vital teeth and the orthodontic in situ model for slabs of enamel, root surface, dentin, or other mineralized tissues such as shark enamel. The model for vital teeth is an in vivo model, since a crevice for plaque accumulation is created behind orthodontic bands on the buccal enamel surfaces of teeth in situ. Visible white-spot lesions are usually seen after a four-week banding period in the absence of fluoride. The microbiological flora developed behind the bands shows a similarity to that of natural caries. Microradiographic data show that the initial lesion is a softening of the enamel surface. Later, a subsurface lesion develops. A modification of the model has been developed for the use of slabs of mineralized tissues. In this model, slabs are mounted on a removable appliance. The slabs are covered with orthodontic banding material for plaque accumulation. Lesion development in enamel in the two model systems is almost identical. The benefit of the in vivo model is that caries development can be studied on vital teeth in young individuals. The model is independent of the patient's cooperation. No special diet is required, e.g., no sucrose rinsing. In the in situ model, slabs could be examined after one study period and then replaced for another period.

Dental Caries↗
PubMed1992

Intra-oral models: comparison of in situ substrates.

Numerous intra-oral caries models have been designed for clinical and mechanistic purposes. Several factors--such as human vs. bovine enamel, sound vs. demineralized tissues, lesion type, dentin vs. enamel, the severity of the cariogenic challenge, and the microflora--may influence the reactivity of the hard tissue and hence lesion development and progression. Some models use unextracted teeth and are true in vivo models, whereas in situ models are based on hard-tissue substrates in the form of slabs or sections. Models producing a moderate cariogenic challenge usually show a fluoride dose response. However, caries is increasingly becoming a problem limited to some high-risk patients and to lesions located to areas where severe challenges exist (e.g., fissures and pits). There is thus need for models that could mimic such situations. One of the requirements for intra-oral models producing severe cariogenic challenge conditions should probably be that it should be able to demineralize fluorapatite. A challenge for future caries research is to develop agents that have a better clinical effect in fissures and pits than those presently available. Because, in the past, much emphasis has been placed on remineralization of artificial lesions, more research on the demineralization process should be performed in the future, since this may give improved clinical effects. Ideally, an intra-oral caries model should take into account as many of the natural oral conditions as possible and minimize the degree of artificiality.

Animals↗
PubMed1990

Improvement of gingival health by toothbrushing in individuals with large amounts of calculus.

Dental calculus itself is not thought to affect gingival health, but its rough and porous surface retains plaque better than a calculus-free surface. In a population with a high degree of supragingival calculus, the effect of toothbrushing after a careful professional prophylaxis (group A) has been compared with the effect of toothbrushing as the sole oral hygiene aid (group B). The subjects in this comparison were Indonesian soldiers, 20-25 years of age, none of whom had pathological pockets (CPITN less than or equal to 2), but all had large amounts of calculus. They had no experience of modern oral hygiene practice but were given individual instruction in toothbrushing at the start of the study and were provided with toothpaste and toothbrush. Removal of calculus in group A took an average of 1 h per subject by an experienced clinician. Gingival health in both groups improved after 2 months: group A from 63% to 34% bleeding points and group B from 61% to 36%. There was thus no obvious benefit from the professional prophylaxis received by group A. The results are particularly relevant for populations in which professional prophylaxis is not normally available. However, they were obtained in a group of young, healthy individuals and may not be extrapolated to older and less healthy populations or to individuals with deep periodontal pockets. The improvement of gingival health through toothbrushing, in spite of the presence of calculus, supports the contention that plaque, rather than calculus as a non-inflammatory scale, provides the pathogenic potential.

Adult↗
PubMed1990

Relative cariostatic effects of KOH-soluble and KOH-insoluble fluoride in situ.

The relative cariostatic effects of fluoride as fluorapatite, CaF2, loosely-bound fluoride, or KOH-soluble fluoride are debated. The present study was carried out to investigate this further in an intra-oral caries model. Pairs of premolars extracted for orthodontic reasons were used. Enamel from one tooth of each pair was used as control (untreated). Two slabs were cut from the enamel of the other contralateral premolar. These slabs were treated with 2% NaF for 24 h. One slab was then treated with 1 mol/L KOH twice for 24 h for removal of all loosely-bound fluoride. The slabs treated with 2% NaF and then with 1 mol/L KOH would contain the KOH-insoluble fluoride. Those treated with only 2% NaF would, in addition, contain KOH-soluble fluoride. Each slab, control, KOH-insoluble F, and KOH-soluble and insoluble F was mounted on different upper removable appliances. The slabs were covered with orthodontic banding material, thus allowing space for plaque accumulation. Five individuals wore the appliance in three separate four-week periods. The slabs were analyzed by quantitative microradiography. The average mineral loss (delta Z) was 1680 +/- 1000 vol% x microns in the control teeth, 620 +/- 76 vol% x microns in the KOH-soluble and -insoluble F teeth, and 2167 +/- 1278 vol% x microns in the KOH-insoluble F teeth. The average lesion depths were 90 +/- 41 microns in the control teeth, 35.3 +/- 5.5 microns in the KOH-soluble F teeth, and 88 +/- 35 microns in the KOH-insoluble F teeth. It was concluded that only KOH-soluble fluoride reduced mineral loss and lesion depths significantly, compared with the untreated teeth.

Calcium Fluoride↗
PubMed1990

Critical evaluation of the composition and use of topical fluorides, with emphasis on the role of calcium fluoride in caries inhibition.

There is evidence that a major part of the fluoride which is retained on teeth during topical application is calcium fluoride or calcium fluoride-like, and that this material is relatively stable in the mouth. This is due to surface adsorption of phosphate (HPO4(2-)) ions onto the calcium fluoride surface. Calcium fluoride releases fluoride during caries challenges due to reduced concentration of HPO4(2-) at acid pH. Normally, the fluoride released from calcium fluoride during caries challenges is subsequently built into hydroxyfluorapatite through dissolution/re-precipitation reactions. It appears likely that the formation of calcium fluoride from topical application agents should be increased and not reduced, as believed in the past. Increased deposition of calcium fluoride can be achieved with increased reaction time between fluoride and enamel, reduced pH of the solution, increased concentration, or pre-treatment with calcium. A reduction in pH of the agents is probably the most practical approach to increase the deposition of calcium fluoride during topical application, and clinical data support this contention. Calcium fluorides with various dissolution rates are formed during different procedures of topical application with fluoride, presumably due to incorporation of phosphate into the calcium fluoride crystals.

Animals↗
PubMed1990

[Simple model explaining the caries inhibiting effect of fluoride].

The pH at which enamel dissolves is affected by presence of fluoride in the plaque fluid. It appears that the degree of oral hygiene will also be important because pH can drop so low in old plaque that even solid fluorapatite dissolves. Improved oral hygiene would thus reduce caries in high risk patients even in the presence of fluoride.

Dental Caries↗
PubMed1990

[Xylitol, mechanisms of action and uses].

Xylitol is recommended as a sugar substitute and is claimed not only to be non-cariogenic, but also to exhibit an anti-caries effect. An interesting aspect of xylitol is that it has a certain bacteriostatic effect. Xylitol is taken up by many strains of Strep mutans and Strep sanguis even if these organisms are unable to metabolize xylitol. It enters the bacteria by the phospho-transferase system. Xylitol-phosphate inhibits the glycolysis probably at the phosphofructokinase level, and is also de-phosphorylated and expelled through a "futile cycle". The combination xylitol and sorbitol is particularly interesting, since xylitol inhibits the metabolization of sorbitol by Strep mutans and sorbitol also appears to potentiate the bacteriostatic effect of xylitol. Furthermore the combination is favourable from an economical point of view since sorbitol is less expensive than xylitol. Xylitol induces diarrhea if consumed in considerable amounts and is thus only suitable in products like chewing gum and tablets.

Dental Caries↗
PubMed1989

Interaction between chlorhexidine digluconate and sodium lauryl sulfate in vivo.

Chlorhexidine (CH) is cationic and it forms salts of low solubility with anions such as phosphate, sulfate and carboxyl. Toothpastes contain anionic detergents, one of the most widely used being sodium lauryl sulfate (SLS). The aim of the present study was to examine the possible interaction between CH and the anion SLS in vivo. The interference of SLS on the antiplaque potential of CH was investigated. The study was performed according to a single blind cross over design, and the effect of the interval between prerinsing with an aqueous solution of SLS and the subsequent rinsing with CH was examined. The antiplaque effect was examined by the use of the Silness and Löe plaque-index. The results showed that even a 30-min interval between SLS- and CH-rinsing gave a significantly reduced antiplaque effect of CH, whereas the neutralizing effect of SLS disappeared after 2 h. It can thus be concluded that SLS is not compatible with CH, even when these compounds are introduced separately in the oral cavity. The time between toothbrushing and a CH rinse should at least be 30 min, if a reduction in the antimicrobial effect is to be avoided.

Adult↗
PubMed1989

Kinetics of acquisition and loss of calcium fluoride by enamel in vivo.

Two in vivo experiments were performed, concerning (1) the kinetics of the acquisition of calcium fluoride on enamel during daily rinses with a solution of 0.023% F as sodium fluoride, and (2) the loss of calcium fluoride from enamel slabs which had been topically treated with a neutral solution containing 0.9% F as sodium fluoride. Enamel slabs were carried in the mouth by 6 volunteers for 8 days in both experiments. Sound and etched enamel were included. (1) During mouthrinses moderate amounts of fluoride were acquired by sound enamel, and more as calcium fluoride than as fluoridated apatite, whereas on etched enamel, more fluoride was deposited as fluoridated apatite. On etched enamel there was also a tendency that the deposition of calcium fluoride levelled out whereas the incorporation of firmly bound fluoride continued. This may indicate that calcium fluoride was transformed into fluoridated apatite, probably through remineralization during pH cycling in plaque covering the etched enamel. (2) After single topical application, it was found that etched enamel initially took up more calcium fluoride than sound enamel, but also lost more during the 1st day of in vivo exposure. The loss of calcium fluoride was arrested after 1-2 days, on sound enamel at 70% and on etched enamel at 40% of the original level. It is suggested that the increased amounts of firmly incorporated fluoride in enamel originated from calcium fluoride on enamel, and that calcium fluoride is an important and clinically significant source of fluoride ions on enamel.

Acid Etching, Dental↗
PubMed1989

Protein adsorption to hydroxyapatite and to calcium fluoride in vitro and amino acid analyses of pellicle formed on normal enamel and on calcium-fluoride-covered enamel in vivo.

Fluoride treatment of enamel has been reported to result in the formation of a layer of a CaF2-like material on the enamel surface. Protein adsorption to enamel is a specific process dependent on the nature of the surface, and little is known about protein adsorption to CaF2. Albumin and lysozyme were adsorbed to hydroxyapatite (HA) and CaF2 powder in vitro, and protein adsorption patterns constructed. In vivo pellicle was collected from three volunteers from fluoride-treated enamel and from normal enamel, and the amino acid compositions analyzed separately. The results showed that CaF2 took up small amounts of proteins as compared with HA. When the CaF2 was pretreated with a phosphate buffer, pH 6.8, the protein adsorption increased markedly. The amino acid analyses showed no major differences in the amino acid compositions between pellicle collected from CaF2-covered enamel and pellicle collected from normal enamel. This lack of difference is presumably due to the adsorption of phosphate ions to the CaF2 crystals and hence changed surface properties.

Adsorption↗
PubMed1988

Orthodontic appliances and enamel demineralization. Part 2. Prevention and treatment of lesions.

Clinical experiments were performed to investigate the effect of fluoride on carious lesion development and on lesions established during fixed orthodontic therapy. All presently available fluoride agents are developed from the concept of fluoridating the enamel in the form of fluorhydroxyapatite. Recent research has indicated, however, that calcium fluoride formation may be a major aspect of the mechanism of the cariostatic effect of topical fluoride. Therefore a fluoride solution with very low pH (1.9) that induced large amounts of calcium fluoride also was tested on lesion development underneath orthodontic bands. Daily fluoride mouth rinsing with a 0.2% solution sodium fluoride (NaF) retarded lesion development significantly, whereas the fluoride solution with low pH inhibited lesion formation completely. Fluoride applied as a mouth rinse to plaque-covered lesions underneath orthodontic bands retarded lesion progression. The remineralizing capacity of saliva was found to be rapid in the absence of any fluoride. Although white spot lesions may remineralize and even disappear, most of the emphasis should be directed against prevention of carious lesion development during treatment with fixed orthodontic appliances.

Adolescent↗
PubMed1988

Orthodontic appliances and enamel demineralization. Part 1. Lesion development.

A clinical trial was conducted to investigate carious lesion development associated with fixed orthodontic therapy. Specially designed orthodontic bands for plaque accumulation were attached to premolars scheduled to be extracted as part of an orthodontic treatment. Visible white spot lesions were seen within 4 weeks in the absence of any fluoride supplementation. Both microradiographic and SEM examinations showed surface softening of the enamel surface--that is, a surface layer was not seen in the lesions. The clinical significance of the present study is that enamel demineralization associated with fixed orthodontic therapy is an extremely rapid process caused by a high and continuous cariogenic challenge in the plaque developed around brackets and underneath ill-fitting bands. Careful inspection of the appliance at every visit and preventive fluoride programs are therefore required.

Adolescent↗
PubMed1988

Effect of sodium lauryl sulfate on the deposition of alkali-soluble fluoride on enamel in vitro.

There are indications that sodium lauryl sulfate may reduce the cariostatic effect of fluoride when present together with sodium monofluorophosphate during topical application. The aim of the present study was to examine the in vitro deposition of alkali soluble fluoride on enamel during topical application with sodium fluoride in combination with sodium lauryl sulfate. It was found that increasing amounts of lauryl sulfate decreased the amount of alkali soluble fluoride deposited on the enamel. The amount of fluoride deposited from toothpaste supernatants was less than that from aqueous solutions of NaF with the same concentration of fluoride. Enamel pieces, pretreated with sodium lauryl sulfate showed a reduced deposition of alkali-soluble fluoride after incubation in a fluoride solution. It was also observed that the presence of lauryl sulfate increased the solubility of CaF2 in water.

Administration, Topical↗
PubMed1988

In vivo progress of enamel and root surface lesions under plaque as a function of time.

This paper deals with enamel and root surface demineralization under plaque in vivo as a function of time. The enamel was demineralized using the Ogaard method in which preformed orthodontic bands are attached to the premolars in situ for 4, 6, and 8 weeks; a niche in the bands is responsible for plaque accumulation. In a second experiment cement-covered root surfaces (and enamel) were mounted on a removable appliance (Hawley retainer). Also in this case an orthodontic band was placed over the samples to create a space for plaque accumulation of about 0.8 mm between sample and band. All samples were analyzed by means of microradiography. The results show that (1) demineralization of enamel with the Ogaard method and using the Hawley retainer gives values for lesion depth and mineral loss that are statistically not significantly different; (2) lesion progress and mineral loss in vivo is about 2.5 times faster in roots than in enamel; (3) the demineralization in enamel is roughly linear with time, and (4) roots demineralize in vivo very fast during the 1st week and much more slowly there after.

Dental Caries↗
PubMed1988

On the role of calcium fluoride in the cariostatic mechanism of fluoride.

The literature concerning the formation and stability of CaF2 in the oral environment is reviewed. In early work the CaF2 formed during topical application with fluoride was assumed to be beneficial. It was suggested that it could protect the enamel surface directly or provide free fluoride ions for subsequent incorporation into the hydroxyapatite lattice. However, McCann claimed, in 1968, that CaF2 is soluble in saliva (12-15 mg/l), that it would be rapidly lost in the oral cavity, and that the clinical effect of fluoride was related to formation of firmly bound fluoride only. In this period many authors reported total loss of CaF2 during 24 h after a topical application of fluoride. It has now been shown in several laboratories that calcium fluoride is stable in saliva at neutral pH owing to surface adsorption of HPO2-4 to the crystal surface and formation of a solubility-limiting phase. Extended exposure of saliva can cause formation of a fluorapatite layer on the CaF2 crystals, restricting their dissolution further. Low pH (pH less than 5) causes loss of the solubility-limiting adsorbed HPO2-4 and a slow dissolution of CaF2. The CaF2 crystals may thus serve as pH-controlled reservoirs of fluoride ions on the enamel or in plaque and release fluoride during caries challenges. It is suggested that calcium fluoride is an essential phase explaining important aspects of the mechanism of topically applied fluoride, contrary to what was assumed in the past.

Calcium Fluoride↗